#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
int main()
{
	double N;
	cin >> N;
	double sum = 0;
	for (int i = 1; i <= N; i++) {
		double a = 1 / (double)i;
		sum += a;
	}
	printf("%.6lf", sum);
	return 0;
}